Oil cooler



E. GARNER OIL COOLER July 4, 1944.

Filed Oct. 4, 1940 5 Sheets-Sheet l E. GARNER July 4, 1944.

OIL COOLER Filed Oct. 4, 1940 3 Sheets-Sheet 2 V E. GARNER July 4, 1944.

OIL COOLER Filed 001;. 4, 1940 a sheets-sheet 5 Patented July 4, 1944 UNITED STATES PATENT OFFICE 2,352,704 OIL COOLER Edward Garner, Greet, Birmingham, England,

assignor to Serck Radiators Limited, Birmingham, England- 3 Claims.

This invention relates to oil coolers of the type in which oil is caused to traverse passages formed by the outer surfaces of tubes through which air or liquid coolant passes, and particularly coolers of this type adapted for use on aircraft.

The object of the invention is to provide an improved cooler whereby risk of excessive cooling of part of the oil within the cooler is minimised, and whereby rapid warming of the oil in a cold cooler is conveniently obtained.

The invention comprises the combination of a plurality of groups of coolant tubesone of which groups is situated centrally between the others, an oil inlet connection associated with the entrance to the central group, an oil outlet connection associated with the exit from at least one of the other groups, and means whereby oil from the central group can pass through the other groups to the said outlet connection.

The invention also comprises a cooler as specifled in the preceding paragraph and having combined with it a valve-controlled by-pass situated between the exit end of the central group of tubes and the outlet connection.

Further the invention comprises a cooler as specified in the preceding paragraph and having combined with it another valve-controlled icy-pass situated between the inlet and outlet connections.

In the accompanying sheets of explanatory drawings:

Figure 1 is a diagrammatic sectional end elevation of an oil cooler constructed in accordance with the invention for use on air-craft.

Figure 2 is a sectional view illustrating diagrammatically a modified partition arrangement, and Figure 2a. is a section on the line A-B of Figure 2. p

Figure 3 is a similar view illustrating diagrammatically a further modified form of the invention.

Figure 4 is a similar view illustrating diagrammatically a still further modified partition arrangement.

Figures 5 and 6 are respectively a part sectional end elevation and a part sectional side elevation of a preferred form of an oil cooler constructed in accordance with the invention for use on air-craft.

In carrying the invention into effect as shown in Figure 1, I employ a cylindrical sheet metal casing 11 which is open at both ends. Within this casing are mounted three groups of tubes, namely a group of tubes b situated centrally between two side groups of tubes 0. The tubes b, c are formed with expanded hexagonal or other polygonal ends (as shown in Figure 5), and are assembled in the usual manner to form between their outer surfaces narrow passages for the oil. The air required for cooling the oil flows longitudinally through the tubes b, c and the ends of the casing a.

The central group of tubes 1) extends diametrically across the'interior of the casing a, andthe other two groups of tubes 0 occupy the spaces within the casing at opposite sides of the central group. The central group of tubes 2) is sepa rated from the side groups of tubes 0 by thin sheet metal partitions e. The oil may be caused to take a transverse zig-zag course through the side groups of tubes 0 by thin sheet metal partitions f arranged at right angles to the other partitions e and extending alternately from the latter and from. the inner surface of the casing a.

Within the casing a there is formed at the entrance end of the central group of tubes b a space g extending over the entire length of this end, and in communication with this space there is mounted on the exterior of the casing an oil inlet connection h. Also within the casing a at the exit end of each of the two side groups of tubes 0 is formed another space i extending over the whole length of the said end, and these two spaces communicate through passages 7 with a common outlet connection is mounted on the exterior of the casing.

Around the exterior and extending over the whole or the greater part of the length of the casing 11 is an annular passage m, this being bounded at its inner side by the casing and at its outer side and ends by a sheet metal shell 12. The passage 111. communicates through an opening or openings as o in the casing a with the exit end of the central group of tubes 12, and through openings p in the casing with the entrance end of the side groups of tubes 0. It will be seen therefore that the side groups of tubes c are arranged in parallel between the exit end of the central group of tubes b and the outlet connection is.

Oil entering the inlet connection h first passes between the tubes 1) in the central group. On reaching the exit end of this group of tubes the oil enters the passage m around the casing a through the opening or openings as o in the casing. The oil stream then divides and passes to the entrance ends of the side groups of tubes 0 through the openings 21 in the casing a. Finally the oil passes between the tubes in the side groups to the outlet connection It.

Such a cooler is used for cooling the lubricating oil of an air-craft engine. On starting up the cooler may be cold and the viscosity of the oil in the cooler may be high. By causing warmed oil from the engine to pass through the central group of tubes b, the oil between the tubes 0 in the other groups quickly becomes warmed and its viscosity correspondingly reduced more quickly than in coolers of ordinary construction. Excessive heating is prevented by the cooling action of the air flowing through the tubes b, c.

When an air-craft is flying at high speed in cold regions it has been found that an oil cooler of ordinary construction is apt to cause excessive cooling of the oil occupying a central region in the cooler, with the result that the whole of the cooler is not effectively used, the less viscous oil passing ineffectively over the cooling surface or taking the path of least resistance around the warmer regions of the cooler. By our invention we gain the further advantage that risk of occurrence of an excessively cold region in the cooler is minimised or obviated, with the result that the whole of the cooler is efllciently utilised.

Preferably and as shown there is arranged between the annular passage m and the outlet connection is, a passage q for by-passing the two outer groups of tubes c until the oil between the latter tubes has become warmed to a predetermined degree by the incoming oil. The by-pass passage q is controlled by a spring loaded or thermostatically actuated relief valve 1'. While the oil between the tubes 0 in the two side groups is cold, the oil from the central group of tubes b flows around the annular passage m and through the valve-controlled by-pass passage q to the outlet connection k. But as soon as the viscosity of the oil in the side groups of tubes 0 'and consequently the resistance to flow falls sufliciently,

the valve 1 in the by-pass passage q closes and oil then flows from the central group of tubes b through the side groups of tubes 0.

Instead of being arranged to cause a transverse zig-zag flow of the oil through the side groups of tubes 0, the partitions I may be arranged as shown in Figure 2 to cause a longitudinal zig-zag flow of the oil through these groups of tubes. In this example the partitions I extend completely across the spaces between the group partitions e and the casing a, and are formed near alternate ends with openings 8 through which the oil can flow. In other respects the example shown in Figure 2 is similar to that shown in Figure 1, the corresponding parts of the two examples being indicated by the same reference characters.

The example shown in Figure 3 enables the oil from the central group of tubes b to flow in series through the side groups of tubes 0 instead of in parallel as above described. In this example the entrance end of one of the side groups of tubes 0 communicates with the annular passage m around the casing a throlmh an opening or openings as t formed in the casing at a position,

remote from the opening or openings as 0 con-- necting the said passage to the exit end of the central group of tubes b. Also the exit end of this side group of tubes 0 is connected to the entrance end of the other side group of tubes by a passage u passing through the annular passage m. Further the exit end of the latter side group of tubes is connected to the outlet connecalso connected to the annular passage m through a by-pass passage w controlled by a relief valve 1' as above described. It will be seen therefore that the side groups of tubes 0 are arranged in series between the exit end of the central group of tubes b and the outlet connection k. As in the previous examples oil entering the inlet connection h first passes between the tubes b of the central group, and on reaching the exit end of this group enters the annular passage m arolmd the casing a. Also, if the oil between the tubes c of the two side groups is cold, the oil entering the annular passage m from the central group of into the corresponding side group of tubes c. v

After passing through this side group of tubes c the oil flows through the connecting passage 1; and the other side group of tubes 0 to the outlet connection It.

As in Figure 1 the partitions j employed in the example shown in Figure 3 cause a transverse zig-zag flow of oil through the side groups of tubes 0, but if desired these partitions may be be arranged as shown in Figure 4 to cause a longitudinal zig-zag flow of the oil through these groups of tubes. Apart from the partitions I, which are similar to those shown in Figure 2, the example shown in Figure 4 is essentially the same as that shown in Figure 3, the same reference characters being employed in each case to indicate corresponding parts.

In all of the coolers shown in Figures 1 to 4 the normal paths of the oil are indicated by arrows shown in full lines, and the paths of the oil to the by-pass valves r are indicated by arrows shown in broken lines.

As shown in Figures 5 and 6, a pair of coolers are connected in series with each other. The casings a of the coolers are secured together in coaxial relationship by a metal strap 11 encircling a pair of complementary half-rings 2 secured respectively to the adjacent ends of the casings, the ends of the strap being secured together by a clamping bolt 2 or other fastening. Also the outlet connection k of one of the coolers (the one on the left in Figure 6) is secured to and communicates with the inlet connection h of the other cooler. As the two coolers are of essentially similar form only one will be described. The partition plates e separating the central group of tubes b from the side groups of tubes c are made of corrugated form to accommodate the expanded hexagonal or other polygonal ends of the tubes. The inlet connection h and the outlet connection k are formed by opposite ends of a hollow casting 3 and are separated by a partition ii in the casing. The latter contains the relief valve r which co-operates with a seating 4 in the interior of the casting 3 for controlling communication between the outlet connection It by a passage 11, the outlet connection being Is tion I: and the annular passage m around the casing a, this passage being bounded at its outer side and ends by a sheet metal shell 1: as previously described. The relief valve 1' is loaded by a spring 5 or any convenient thermostatic means. The inlet connection h communicates with the space 9 at the entrance end of the central group of tubes b. The annular passage m communimates with the exit end of the central group of tubes b through the previously described opening in the casing, and with -a space 0 at the entrance end of one otrthe side groups of tubes c through another opening t formed in the casing at a position'remote from the opening 0. Also a space I at the exit end 01' this side group of tubes 0 communicates with a space 8 at the adjacent and entrance end of the other side group of tubes c through a passage u made from sheet metal and passing through the annular passage m. Further a space 9 at the exit end of the latter side group of tubes c is connected to the outlet connection It by another passage 1) made from sheet metal and passing through the passage m. The arrangement of the openings as t and passages 12 of the two coolers is such that the oil from the two central groups of tubes as b passes through the corresponding annular passages m to opposite side groups of the tubes is 0.

Preferably and as shown the hollow casting 3 of each cooler contains in addition to the relief valve r another relief valve of any convenient form, this being situated between the inlet and outlet connections h, Is. As shown the valve ii is loaded by a spring l2 and co-operates with a seating I 3 around a bY-pass opening ll in the partition it which separates the inlet connection it from the outlet connection k. While the oil between the tubes b in the central group is cold, the pressure of the oil entering the inlet connection It causes the relief valve Ii to open and allow some of the oil to flow from the inlet connection to the outlet connection is through the by-pass opening it. But as soon as the viscosity of the oil, and consequently the resistance to oil flow, between the tubes b falls sumciently the relief valve ll closes and all of the oil from the inlet connection h flows between these tubes. The spring loading of the relief valve II is made sufiiciently greater than that of the other relief valve 1' to prevent the valve H from being opened by the resistance to oil flow between the tubes b in the side groups.

By this invention rapid warming of the oil in a cold cooler, and the reduction of risk of localised excessive cooling of oil when the cooler is in action, is efiected in a very simple and satisfactory manner.

Whilst the invention is primarily intended for use on air-craft it is not limited thereto as it may be applied to other uses. Moreover, water or other liquid may be used as the coolant by providing inlet and outlet headers at the ends of the casing.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

l. A device or the class described comprising outer and inner circular in cross section cylinders arranged one within the other and secured together to form an annular chamber, two partitions in said inner cylinder extending from one side to the other thereof forming an oil passageway, said passageway having an inlet at one end and an outlet to said annular chamber at the other end, tube chambers on either side of said oil passageway having openings for admitting oil from adjacent the other end of said oil passageway, said tube bundles also having out-- lets connected together forming a single outlet, bundles of tubes in said tube chambers having means forming tube plates and end closures for said chambers. a connection from said annular chamber adjacent said inlet and extending to said single outlet, a relief valve positioned in said connection and arranged to open when the oil will not pass between the tubes in said tube chambers to thereby permit the oil to pass directly through said oil passageway and annular chamber to said single outlet.

2. An oil cooler comprising the combination of a plurality of groups of coolant tubes, each group having oil passages formed by the outer surfaces of its tubes, a casing in which said groups are mounted with one group situated centrally between the others, an inlet connection whereby oil can flow to the central group, an outlet connection whereby oil can flow from at least one of the other groups, means including a passage situated around said casing whereby oil from said central group can flow through the other groups to said outlet connection, and a valve-controlled by-pass situated between said passage and outlet connection.

3. An oil cooler comprising the combination of three groups of coolant tubes, each group hav-' ing oil passages formed by the outer surfaces of its tubes, a casing in which said groups are mounted with one group situated. centrally between the others, partitions separating said groups, an inlet connection whereby oil can flow to the central group, an oil outlet connection whereby oil can flow from one of the other groups, a passage interconnecting the latter groups, an annular passage situated around said casing, the latter being formed with ppenings which together with the two passages enables oil from said central group to flow in series through the other groups to said outlet connection, and a valve-controlled by-pass situated between said annular passage and outlet connection.

EDWARD GARNER. 

